Hf-bf3 isomerization of poly-secondary alkylbenzenes



United States Patent HFBF ISOMERIZATION OF POLY-SECONDARY ALKYLBENZENES Arthur P. Lien, Highland, Ind., and David A. McCaulay,

Chicago, Ill., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Original application October 30, 1953, Se-

rial No. 389,328. Divided and this application June 8, 1956, Serial No. 590,104

11 Claims. (Cl. 260-668) This invention relates to the rearrangement of certain secondary alkylbenzenes. More particularly the invention relates to the disproportionation of isopropylbenzene and secondary butylbenzene. Still more particularly the invention relates to the production of essentially pure meta di-isopropylbenzene and 1,3,S-tri-isopropylbenzene.

The development of the hydroperoxide synthesis for phefnol has resulted in a demand for secondary alkylbenzenes. Since certain phenols have particularly desirable properties for use as chemical intermediates, a demand has arisen for large quantities of various secondary alkylbenzenes of high purity, i. e., about 95%, and also essentially pure, i. e., 99%, compounds. Of particular interest are meta di-isopropylbenzene and 1,3,5-tri-isopropylbenzene. The production of di-isopropylbenzene by the alkylation of benzene with propylene produces a mixture of the three isomers; therefore, industry is concerned with the preparation of high purity individual isomers in high yield.

It is an object of this invention to prepare di-secondary alkylbenzenes by the treatment of isopropylbenzene or secondary butylbenzene. Another object is the production of tri-secondary alkylbenzene by the treatment of the corresponding secondary alkylbenzene or di-secondary alkylbenzene. Still another object is a process for the conversion of secondary alkylbenzene to high purity meta di-secondary alkylbenzene without simultaneously producing any significant amount of tri-secondary alkylbenzene.

Yet another object of the invention is a process for the production of high purity meta di-secondary alkylbenzene fr'om a feed containing at least one of the other isomers or mixtures of the meta isomer and substantial amounts of the other isomers. A further object is a process for the preparation of high purity meta di-secondary alkylbenzene without the simultaneous production of significant amounts of tri-secondary alkylbenzenes. A specific object is the preparation of essentially pure meta di-isopropylbenzene by the treatment of a mixture of diisopropylbenzene isomers Without simultaneously producing-= any appreciable amount of tri-isopropylbenzenes. Other objects will become apparent in the course. of the detailed description of the invention.

DISPROPORTIONATION at a temperature between about -30 C. and about +80 C. for a time at least suflicient to permit an appreciable amount of rearrangement reaction; the HF and BF; are removed from the acid phase in order to recover polysecondary alkylbenzene.

By operating for a sufliciently short time at a temperature between about -30 C. and about 5 (3., production of tri-secondary alkylbenzene can be essentially eliminated. Operation at temperatures below about 30 C. substantially halts the disproportionation reaction.

The charge to the disproportionation process contains secondary alkylbenzenes selected from the class consisting of isopropylbenzene and secondary butylbenzene. In order to obtain products containing only one particular alkyl substituent, the feed must contain essentially only either isopropylbenzene or secondary butylbenzene as the reactive component.

In addition to the secondary alkylbenzene, the feed may contain non-reactive liquid hydrocarbons. It is to be understood that the term non-reactive liquid hydrocarbons is intended to mean those hydrocarbons which are liquid at operating conditions and which are inert to the action of the HF-BF agent and do not participate in any reaction with the secondary alkylbenzene charged. Examples of reactive hydrocarbons are olefins, xylene, diethylbenzene, ethyltoluene, ethylbenzene and isopropyltoluene. Examples of non-reactive hydrocarbons are: Isopentane, butane, and hexane. It is preferred that benzene be absent from the feed as its presence has an adverse etfect on the degree of disproportionation obtained.

The process utilizes substantially anhydrous liquid hydrogen fluoride. The liquid hydrogen fluoride should not contain more than about 2 or 3% of water. Commercial grade anhydrous hydrogen fluoride acid is suitable for this process.

Under the conditions of the process, polyalkylbenzenes form a complex containing 1 mole of BF and, it is believed, 1 mole of HF per mole of polyalkylbenzene. Therefore, at least enough liquid HF must be present to participate in the formation of the complex with the poly-secondary alkylbenzene; in addition to this amount, sufiicient liquid HF must be present to dissolve the complex which has been formed. In general, the presence of a distinct separate acid phase in the contacting zone indicates that at least the minimum requirement ,of liquid HP has been met. More than this minimum amount of liquid HP is desirable. Usually between about 3 and 50 moles of liquid HF are utilized per mole of secondary alkylbenzene charged to the process. It is preferred to operate with between about 5 and 20 moles of liquid HF per mole of secondary alkylbenzene charged.

The process requires the presence of at least an amount of boron trifiuoride sufficient to cause a rearrangement reaction to take place, specifically the disproportionation of the secondary alkylbenzene to'poly-secondary alkylbenzene. While amounts of BF as small as 0.1 mole per mole of secondary alkylbenzene charged will cause an appreciable amount of rearrangement reaction to take place, it is desirable to operate with about 0.3 mole of BF Still more BF has a beneficial effect on the degree of the rearrangement reaction and as much as 5 or more moles may be used. When high purity meta di-secondary alkylbenzene is a desired product, at least 0.5 mole of BF should be used per mole of secondary alkylbenzene charged, and it is preferred to use between about 1 and about 2 moles of ER; per mole of secondary alkylbenzene charged, for example, 0.9 mole.

When the feed to the process contains poly-alkylbenzenes in addition to the secondary alkylbenzene, 1 mole of BB, should be used per mole of said poly-alkylbenzene, in addition to that set out above.

-The process may be operated with two liquid phases present in the contacting zone. At high BF usages, a gas phase may also be present in the contacting zone. The two liquid phases will be spoken of herein as the raflinate phase and the acid phase. The acid phase consists of liquid HF, BP complex and physically dissolved hydrocarbons. The raffinate phase may be secondary alkylbenzenes in excess of that amount taken into the acid phase, or may be a mixture of secondary alkylbenzene and inert hydrocarbons, or may be principally inert hydrocarbons. In the absence of substantial amounts of inert hydrocarbons, the amount of raflinate phase is dependent upon the amount of BP utilized. When using at least about 0.5 mole of B1 per mole of secondary alkylbenzene, and in the substantial absence ofinert hydrocarbons, all or virtually all the secondary alkyibenzene will be taken into the acid phase either in the form of a complex or in solution. The presence of HF-BFQ poly-alkylbenzene complex in liquid HF very greatly increases the solubility of the liquid HF for aromatic hydrocarbons and increases slightly the solubility of paraffinic hydrocarbons.

The presence of a raflinate phase consisting principally of inert hydrocarbons, such as benzene and paraflins, has an adverse effect on the degree-and direction of conversion of the secondary alkylbenzene charged, even though theoretically sufiicient BF is present to complex all of the poly-secondary .alkylbenzene formable from the secondary alkylbenzene charged. A substantial amount of the secondary alkylbenzene will remain in the raflinate phase, even when using somewhat more than 0.5 mole of B1 per mole of secondary alkylbenzene charged. The secondary alkylbenzene in the raflinate phase does not undergo a rearrangement reaction to any significant extent, even under conditions of good agitation. The pres ence of dissolved inert hydrocarbons in'the acid phase does not appear to have any adverse efiect on the degree or direction of the rearrangement reactions.

In order to maximize the yield of conversion products, and to produce a di-secondary alkylbenzene product fraction consisting essentially of 1,3-di-secondary alkylbenzene, i. e., the meta isomer, it is preferred to operate under conditions which form a singleessentially homogeneous liquid phase in the contacting zone. A single essentially homogeneous liquid phase is attainable with afeed containing as much as three volume percent of parafiinic hydrocarbons. Large amounts of benzene may be dissolved in the acid phase, as much as 1 mole or more, per mole of complexed polyalkylbenzene, depending on the amount of complex in the acid phase. (It is to be understood that a separate gaseous B1 phase may also be present, but it is preferred that a minimum of free space be present in the contacting zone and that sufficient pressure be maintained to insure that essentially all the BB, is either in the complexed form or is in physical solution in the acid phase.)

The degree and direction of the disproportionation reaction are also determined by the temperature of contacting and the time of contacting; a definite relationship exists between the temperature, time and desired disproportionation products. At temperatures below about 40 C. no appreciable disproportionation takes place even at contacting times of several hours. At temperatures of about +100 0, side reactions suchascracking occur and the direction of the dispropo'rtionation changes; gas and a wide boiling range product mixture are obtained. The practical upper limit for the operation of the disproportionation process is about +80 C. Appreciable amounts of disproportionation product are obtained in a not excessively long time at a temperature of about 30 C. The preferred range of operating temperatures for the disproportionation process is between about 20 C. and about +60 C.; wherein the time of contacting is between about minutes and 24 hours, the longer times corresponding to the lower tem peratures.

The contacting time has an important effect on the course of the rearrangement reactions. At least sutficient time must be provided at the particular'temperature of operation in order to obtain an appreciable amount of disproportionation products. As the contacting time is increased, at a constant temperature, the amount of dis proportionation product increases. The disproportionation reaction appears to produce the di-secondary alkylbenzene as the first product. Dependent upon the tempe'rature, a'finite period of time elapses between the appearance of detectable amounts of the di-secondary alkylbenzene product and the appearance of the tri-secondary alkylbenzene product. The lower the temperature of operation, the longer the time" lapse between the appearance of the di-derivative and the appearance of the triderivative.

With increasing contacting-time, at constant temperature, the amount of tri-secondary alkylbenzene product gradually increases at the expense of di-secondary alkylbenzene formed. Gradually the amount of the tri-derivativeincreases and eventually thetri-derivative continues to increase with simultaneous disappearance of the diderivative. At higher temperatures andprolonged contacting times, the'reaction product mixture contains the t'ri-derivativeasthe predominantdisproportiohation reaction-product.- Howe'ver,-even at C. and prolonged contacting times,-somesecondary alkylbenzene and some di-secondary alkylbenzene will be found in the reactionproduct mixture. Thus by adi'usting'the temperature and time of contacting, it is possible to control the relative amounts of di and tr'i-derivatives produced in thedispro-portionation process.-

The 'disproportionation reaction canbe controlled, within experimental error, to produce'di-secondary alkylbenzene a's'es'sentially the'only poly-secondary alkylbenzcne product. When the di-secondar'y alkylbenzene is the only desired poly-secondary alkylbenzene disproportionation product, the contacting temperature should not exceed about -5 C. The lowerter'r'ipe'rature of operation is about 30 C.

The contacting' time at '-5- C. must beshort enough to essentially eliminatethe 'disproportionationto the'triderivative. At about -5 C. the permissible maximum time-of contacting is about 15 minutes to essentially avoid the formation of the tri-derivative. The lower the temperature of contacting, the longer the contacting time permissible for avoiding the formation of detectable amounts of the tri-derivative. At about -20 C. contacting temperature, the permissible maximum-time is on the order of 6 hours; at about -30 C., the permissible maximum contacting time is on the order of a day or more. Thus in order to avoid the formation of appreciable amounts of tri-secondary alkylbenzene, the disproportionation process must be carried out at a'temperature of about 5 C., for a maximum contacting time of about 15 minutes. The lower the temperature of contacting, the longer will be the corresponding permissible maximum contacting time.

Even when using smaller amounts of BF the predomi nant di-secondary alkylbenzene product-is the 1,3-di-secon'dary alklybenzene, i. e., the metaisomer. The use of 0.5 mole of SP and preferably about 1 mole,- gives essentially pure l,3-di-secondary alkylbenzene as the disecondary alkylbenzene product. By careful control of the contacting time, it is possible to'produce a di-secondary alkylbenzene product fraction which is, within the error of the analytical procedure, pure l,3-di-secondary alkylbenzene.

Under the conditions of operation described above, the tri-derivative is essentially pure 1,3,5-tri-secondary alkylbenzen'e, i. e., the symmetrical configuration.

Whenthe charge to the disproportionation process do scribed above is a secondary alkylbenz'ene selected from the class consisting of isopropylbenzene and secondary butylbenzene, the reaction product mixture contains'rel-atively large amounts of the'di-secondary alkyl derivative even though high temperatures and long'co'ntacting times are used. When it is desired to'maxlmize the yield of the tri-secondary-alkylbenzene product. fraction, to charge to the disproportionation process should be the corresponding di-secondary alkylbenzene. The use of an isomer or a mixture of isomers of di-secondary alkylbenzene which are selected from the class consisting of diisopropylbenzenesand di-secondary butylbenzene as the charge to a disproportionation process, wherein sufficient liquid HF and B1 are used to form, a single essentially homogeneous phase, at atemperature between about -2,0 and +60 C. for a suitable contacting time, results in a reaction product mixture wherein the di-secondary alkylbenzene forms only a minor part of the reaction product mixture. In the processwherein the di-derivative is the charge, it is preferred to useat. least 1 mole of, BFg per mole of charge.

When the charge to the di-secondary alkylbenzene disproportionation processconsists of mixtures of the meta isomer and at least one other isomer, whichother isomer is present in substantial amounts, the acidphase contains a reaction product mixture wherein the di-secondary alkylbenzene fraction is enriched with respect to the meta isomer when compared with the charge. When operating under essentially single liquid phase conditions and with at least 1 mole of BF per mole of di-secondary alkylbenzene charged, the reaction product mixture contains essentially pure meta di-secondary alkylbenzene as the secondary alkylbenzene component, i. e., the ortho and/ or para isomers are isomerized to the meta isomer.

The disproportionation at higher temperatures of disecondary alkyl-benzenes produces appreciable amounts of the tetra-derivative as. well as the tri-derivative. Operation at lower temperatures andfor short times permits holding the yield of tetra-derivative to the minimum.

However, when the tetra-derivative is the desired product, it is preferred to operate with the corresponding trisecondaryalkylbenzene as the charge tow the process. Using at least 1 mole of BE, and sufficient liquid HF to form an essentially single homogeneous phase, tri-isopropylbenzene or tri-secondary butylbenzene are disproportionated at temperatures between about +30 C. and about +60 C. and suitable contacting times into a product mixture containing the corresponding tetrasecondary alkylbenzene as the predominant component.

Theinvention is limited to the HF-BF treatment of isopropylbenzene isomers and secondary butylbenzene isomers because successful treatment of the secondary pentylbenzenes requires very different operating conditions. Even at temperatures on the order of +20 C. and contacting times as short as 15 minutes, the secondary pentylbenzenes undergo rearrangement of the pentyl group and also cracking of the pentyl group. In addition, cyclization reactions occur and substantial quantities of indanesand tetralins are formed. Rearrangement of the pentyl group is particularly prominent when 3-phenylpentane is the charge to the HF--BF' contacting zone. The 3-phenylpentane isomerizesto give good yields of the Z-phenylpentane derivative, particularly the 2,4-bis(2- pentyl)benzene disproportionation product. Rearrangement of the pentyl group is not present to any large extent when 2-pentylpentane is the charge to the HF--BF contacting zone. It is to be understood that by suitable adjustment of the temperature and time of contacting it is possible to minimize side reactions.

ISOMERIZATION OF POLY-DI-SECONDARY ALKYLBENZENES The isomerization reaction considered herein is the shift of position of substituent alkyl groups on the benzene ring without rearrangement of the alkyl group itself. The isomerization process comprises contacting, under substantially anhydrous conditions and in the substantial absence of reactive hydrocarbons, a di-secondary alkylbenzene selected from the class consisting of the ortho isomer, the para isomer, and mixtures thereof with at least an efiec- 6 tive. amount; ofjBF and an amount of liquid HF at least sufficient to form adistinct acid phase; the contacting is carried out at a temperature of not more than about --30 C. for about not more than 30 minutes; as the temperature of contacting is lowered, the permissible maximum time of contacting may be increased; and removing HF and BE, from the acid phase under conditions, to substantially avoid rearrangement reactions and recovering from the reaction product mixture a di-secondary alkylbenzene fraction containing the meta isomer. A feed, containing mixtures of the metaisomer and a substantial amount of at least one of the other isomers, when treated with at least'about 1 mole of BF per mole of disecondary alkylbenzene charged, and other conditions as givenv above, produces a reaction mixture enriched with the meta isomer relative to the charge to the process.

By carrying out the isomerization process in the presence of added benzene, the process may be carried out at temperature as high as about 5 C. without producing appreciable amounts of disproportionation reaction products. It is preferred to use at least about 1 mole A of added benzene per mole of di-secondary alkylbenzene charged.

The charge to the low temperature isomerization process contains a di-secondary alkylbenzene selected from the class consisting of the ortho isomer, the para isomer, mixtures thereof, and natural mixtures of all three isomers. When using at least about 1 mole of B1 per molevof di-secondary alkylbenzene charged, the feed may contain mixtures of the meta isomer and a substantial amount least an amount of BP suflicient to cause, an appreciable amount of isomerization of the ortho and para isomers-to the meta isomer. While amounts of BF as small as 0.1 mole per mole of di-secondary alkylbenzene charged cause an appreciable amount of isomerization to take place, it is desirable to operate with more than this amount, e. g., about 0.5 mole of BF As much as 5 or more moles of BF may be used. Increasing the amount of BF has an extremely beneficial etfect on the degree of isomerization obtained. When slightly less than 1 mole of BF per mole of di-secondary alkylbenzene charged is used, e. g., 0.9 mole, the reaction product mixture contains high purity meta di-sec-ondary alkylbenzene as the di-secondary alkylbenzene fraction. in order to obtain the conversion of the di-secondary alkylbenzene charged to essentially pure meta di-secondary alkylbenzene, the process is operated with between at least 1 and about 2 moles of BF per mole of di-secondary alkylbenzene charged.

The isomerization process may be carried out with two liquid phases in the contacting zone as has been described above in the disproportionation process. However, in order to maximize the yield of the isomerization product, and to improve the purity of the desired meta di-secondary alkylbenzene, it is preferred to operate under condi-. tions which form a single essentially homogeneous liquid phase in the contacting zone.

The isomerization reaction considered herein is the shift of position of substituent alkyl groups on the benzene ring without rearrangement of the alkyl group itself.-

This isomerization reaction proceeds at a much faster rate, at lower temperatures, than does the reaction wherem alkyl groups are transferred from one benzene ring to another benzene ring, i. e., disproportionation; It is possible by suitably adjusting the temperature and time of contacting "to essentially avoid the formation of disproportionation products and limit the course of the rearrangement reaction to-isomerization alone. (It is to be understood that the term to essentially avoid is intended 'to mean-within the error of the analytical procedures now available to the art-,for' example, ultra-violet and infrared techniques.) 7

At temperature ofnot'more than about 20 C. it is possible, by limiting the contacting'time to not more than about 30 minutes, to isomeri'zesubstantially all the ortho and/or paraisomers-presentin the charge to the corresponding met'a'isom'er, when'at' least about 1 moleof BF is used permole' of secondary alkyltoluene charged. As the temperature-of contacting is lowered, the permissible time of contacting maybe lengthened without formation of appreciabl'e'amounts of theundesired disproportionation reaction products. When the process is operated at about 3\'- C. for a time of not'more than about 1 5 minutes, the reaction product mixture contains essentially no disproportionation reaction products; at a BF usage of at least 1 mole of BF per mole of di-secondary alkylbenzeue charged, and these conditions of time and temperature, essentially pure meta di-secondary alkylbenzene is obtained as the reaction product;

Obviously operation atthese low temperatures and very short Contacting times has a serious efiect on the commercial practicality of this isomerization process. It has been found that the presence of benzene'in the feed to the process has a remarkable effect on the 'rate at which disproportionationproceeds. The presence of substantial amounts of benzene in the charge slows down the disproportionation reaction rateto such an extent that it is possible to essentially eliminate the products of disproportionation at temperatures where substantial quantitles of the tri-secondary alkylbenzene would have been formed, in the absence of added benzene.

The isomeriz'ationprocess can be carried out without formation of appreciable amounts of disproportionation products at temperatures of not more than about 5 C. when the charge to the process comprises essentially the defined di-secondary alkylbenzene and benzene.

The amount of disproportionation products formed is dependentupon temperature, ti'me'and amount of benzene added; it is preferred to use at least about 1 mole of added benzene and preferably the maximum amount soluble in the acid phase should be used. When operating with about 1 mole of benzene in the feed per mole of (t -secondary alkylbenzene present therein, the isomeriza tlon process may be carried out at about -'-5 C. for an about 5 minute maximum contacting time; at about 0 C. for an about minute maximum contacting time, and at about -'20 C. for art-about 2 hour maximum con tacting time. Under this relationship of temperature and time, and-at least'l mole of BP per mole of secondary alkylbenzene charged, an essentially pure meta di-secondary alkylbenzene product is obtained, without forming any appreciable amount of the corresponding tri-secondary alkylbenzene disproportio-nation'product.

Mixtures of the isomers or the individual non symmetrical isomers of tii-secondary alkyibenzene are isomerized to the symmetricalconfiguration, i. e., 1,3,5-trisecondary alkylbenzene. By the use of at least 1 mole of B1 per mole of tri-secondary alkylbenzene and sufiicient liquid HP to form an essentially single liquid homogeneous phase and a temperature between about 0 and +30 C. and a suitably short time, it is possible to obtain essentially pure 1,3,5-tri-secondary alkyl'c enzene as the reaction product, to the essential exclusion of disroportionation to tetra-secondary alkyl-benzene. By the use of added benzene it is possible to operate at temperatures as high as 0, without substantial dispropoe tionation.

8 PRODUCT RECOVERY The reaction product mixture may be recovered from the acid phase by various methods. Probably the-simplest procedur'e'and oriemost suitable for laboratory work consists of adding the acid phase to crushed ice; or the acid phase may be contacted with cold aqueous alkaline solution, such'a sodium hydroxide, potassium'hydroxide and'ammonia. It isdesirable to prevent rearrangement reactions by the use of a cold aqueous reagent.

The hydrocarbons originally present in the acid phase appear as an upper oil layer above a lower aqueous layer. The upper oil layer'may be separated by decantation and may be 'treated'with dilute aqueous alkaline solution to removeany remaining HF and BB occluded therein.

Both HF and BF are relatively expensive chemicals and it is' desirable in an economic process to recover these and to recycle for reuse in the process. The HP and the BE, 'may bejreadily removed from the acid-phase by heating'the 'ac'id"'phase or by applying a vacuum thereto; The and the BF distill overhead and may berecovered for reuse in the process. When di-alkylbenzenes and/or"tri-alkylbenzenes are the principal complexforming hydrocarbons, the complex may be decomposed at relatively low temperatures by the use of vacuum' distillation. The tetraalkylbenzene and higher alkylbenzene'com'plexes are stable and must be heated to relatively high -temperatures, for example,'l50 C. or more in order to decompose the "complex.

The rearrangement reaction proceeds from the time that the complex is formed until the complex is decomposed,'assuming thatafsuita'ble temperature exists. When it is desired to produce'esse'ntially only one rearrangement"reaction"product, forexample, meta di-isopropylbenzene from'para 'di isopropylbenzene, or meta-di-isopr'op'ylbenzenefromisopropylbenzene, it is necessary to take into account the total time elaps'ing from'the time that the complex has been formed till the time that it has been decomposed in the distillat ive decomposition procedure. Thus, when using distillative decomposition procedure, it is necessary to consider the residence time of the complex in the decomposing zone as a part of the contacting time. Also, it is necessary to consider the temperature maintained in the decomposing zone when av particular 'product or a particular ratio of products is desired. Generally'the temperature in the decomposing zone should be no higher than'that in the contacting zone, when operating to produce meta di-secondary alkylbenzene. The distillative decomposing zone may be operated at temperatures as-10w as about 20" C. by the use of high vacuum therein.

The tri-secondary alkylbenzene at moderate temperatures 'disproportionates very slowly to the tetra-secondary alkylbenzene. Therefore it is possible to distillatively decompose the complex of tri-secondary alkylbenzene at temperatures as high as '40 or 50 C. if the acid phase is very rapidly raisedto that temperature from the reaction temperature and-the'HF and BE, are very'quickly re moved from the heatedacid phase.-

Thusthe recovery 0f the meta 'di-secondary 'alkylben- Zens product without back isomerization to ortlio and para' isomers or'disproportionation to'the tri-secondary alkylhenzene is thernost difiicult recovery to be made by distillative decomposition of the complex. It is obvious that operation at very low temperatures such as lO C. or lower involves an expensive high vacuum operation since liquid HF boils at +20 C. at atmospheric pressure.

The preferred method of recovering high purity meta di-secondary alkylbenzene from an acid phase without back isomerization or disproportionation is the displacement of the meta 'di-secondary alkylbenzene from its HF and BF complex by an alkylbenzene which forms a more stable HF and BE; complex. Broadly, the displacer is a polyalkylbenzene containing at least three alkyl groups which alkyl groups are selected from the 9 class consisting of 'normal and secondaryjand'which contain not more than'4 carbon atoms. Normal alkyl groups are methyl, ethyl, -n-propyl 'and n-butyl. The secondary alkyl groups are isopropyl and secondary butyl.

- place gpreferabiy as a single s'olution; or-the wash hydro earbon m'ay fl be intr'oduced into the acid phase :after the -=addition of "the-dis lacer. 1a order toavoid rearrangement reactions, it is preferred to introduce the wash -hy- Pentamethylbenzene-and hexamethylbenzene are par- "droca'rbon{substantially"simultaneously after the'i-ntroticularly effective displacers. However, the complexes ductionof thedisplacer. formed by these compounds are so stable that quite ele- .It -is preferred to'carry' outthe displacement operation vated temperatures .are necessaryto decomposethe c'omin acontinuous countercurrent tower;-in such an opera plexes in order to recover'the HF and BF Therefore, t-ion, theacidiphaseiis introduced inan upper portion of where economy is desirable,'thesecompounds should not the towerythe displacer'is'introduced at a lower portion be used as displacers. of the tower and th'e cinert wash hydrocarbon is intro- The pre'ferred tri.-alkylbe'nzenes have 'the symmetrical :duced Iat 1a pointlof the tower below the point of entry configuration, i. e.,.1,3,5rtri a1kylbenzene. The preferred of the displacer. tetra-alkylbenzenes possess the 1,2,3,5 configuration. The'amount of inert wash hydrocarbon introduced must 'Thesedisplacersiare preferred becauseithey do not tend 'be-:enoughto remove substantially all the displaced dito undergo rearrangement reactions and have better dissecondary alkylbenzene. In "general, the amount of inert placement efiectivenessthan the other isomers. Theiprewash hydrocarbon used is between about 50 and 500 volferred displacers are mesitylene, triethylb'enzene, tri isoumeypercent. based .on di-secondary alkylbenzene dispropylbenzene, .Ldi-isopropyltoluene and isodurene. .placed, preferably between .about 100 and 250 volume As it is normally'impracticalto 'operateunder condipercent. 'tions wherein absolutely no'tri-secondaryalkylbenzene is In order to avoid rearrangement reactions, the dispro'duced, it is desirable to 'operate'with a displacer'which ,pl-acingi zone should be operated at a temperature and will not complicate the problem of recovering the.byvfor :a'lconta'cting time-such thatessentially no rearrangeproduct, tri-secondary alkylbenzene. Therefore it is,,Pre- .ment: reactions'takeplace therein. Thus, the contacting ferred'to-use as the-displacer in thegprocess of this inventime in-the displacing zone-and the temperature therein "tion 'a poly-secondary alkylbenzene, for example, tri-iso- -m'ust be .considered in determining the total contacting 'propylbenzene, 'or -tri-secondary butylbenzene, corretime=to beutilizedin the;process.

sponding to the alkyl group charged. amples Theoretically, l'mole of added displacer will replace 1 l of id lk lb However,.greate1- .The .resultsobtainable by the invention are illustrated amounts of displacer should be 'used. The amount of hyhevefalvexamples u below- The h e displacer used is dependent upon the total recovery of t e r n Steel reactor p q f Wlth a di-secondary alkylbenzene desiredand also the e'ifective- I 2 T order of addltlon of mate *ness'of the contacting of the acid phase and the displacer. fl t t h e ehmehe y h h It'is preferred to operate with between about 2 and 4 of q y eommefelatghadeanhydrous q t 'moles of'displacer per mole of di-secondary alkylbenzene HF and Commercial grade a- Th Contents of i theackfph-asa the reactor :were agitated during the addit on of the HF v It has been p'ointedout that the acid phase possesses an B3; t e agitatloh wa Continued Whlle the reactor an extremely high solubility for aromatic hydrocarbons. wa u t to the rdesll'ed eohtaetlhg temperature and Q it a large amount fdi la e can b dd d h,: maintained during the contacting time. All the runs 'acid phase Without apparently displacing any di-seconde 'earried 'Ollt Such that y e ary alkylbenzene. By the use of very large amounts of q ldip i :p the reactor at the f p t displacer, it is possible to produce a second liquid phase of the un. The contents of the reactorwere withdrawn whichcomprises displaced di-secondary alkylbenzene and into awessel fined with crushed An pp aqueous di l .hydrocarbon layer .formed above a lower aqueous layer. Since parafiinic hydrocarbons are soluble in the acid e hydrocarbon layer was decanted and washed with phase to only a relatively small extent, it is possible to dilute ammonium hydroXide Solution to remove HF and wash from'the'acid phasetdisplacer-solution the displaced a- The neutral hydrocarbons were water washed to secondary alkylbenzene. The wash hydrocarbonmust be Temove traces of ammonium hydroxideinert to the action of HF and 'BF and non-reactive with 5D The hydrocarbons recovered from the reactor were the k b Present i h id phase. Benzene .fractionatedin .a laboratory distillation column provided may be useda a ash hydroca bon is preferred to With about '[hCOX'CtiCal plates. Each product fraction use as the inert hydrocarbon a low boiling'liquidparafiin awasanalyzedehye-a'eomhthation boiling .P Specific such.as propane, butane, pentane'and hexane. gravity, refractive index, and ultraviolet and infrared The wash hydrocarbon maybe introduced into the hn que. 7 acid phase-displacer"solution simultaneously with'the dis- The results of theseruns are set out in Table I.

TABLE I Run No 1 2 3 4 5 6 7 Charge:

Cumene, moles 2. 5 2. 5 2. 5 2. 5 2. 5 Sec-butylbenzene, moles 1.5 HF/sec-alkylbenzene,.mole ratio. .8 13.8 13.8 14.0 14.0 13. 4 BF /sec-alkylbenzene, mole ratio. 1. 14 1. 08 1. 45 1. 14 1.14 1. 35 Temperature, C +51 +14 20 5 5 +7 Time, Minutes 30 30v 30 5 30 30 Reaction Product Mixture, mole Percent:

Benzene 58.0 53.3 47.5 47 48.1 54.0 Cnmenp 6.3 6.7 5.0 .6 6.2 Sec butylben ene 6.2 m-di-sec-alkylbenzene 13.0 26.7 47.3 47 42.3 25.4 other di-sec-alkylbenzen ome 0.3. 0.1 0.2 0 0 0 1,3,5-trisec-alky1benzene 22.4 13.2 0 0 2.5 14.3 other tri-sec-alkvlbenzene isomers. 0 0 0 O 0 0 .Higher boiling material 0 .0 0 0 0 0 Sec-alkylbenzene conversion, percent" 94 93 95 94 94. 94 Portion going to di-derivative. 28- 57 100 92 56 Portion-going to tri-derivative 72 43 0 0 8 44 Weight basis: Propane, ca 5%;lbenzene,-48%; cumene, 5%; 198218 C.,14%;218253 0., 14%; and tar, 15%.

Run 1 shows that cumene is almost completely converted at +100 C. to a wide boiling range liquid product as well as large amounts of tar, probably condensed ring compounds, and gas.

Run .2, which was similar to run 1 in HF and BF usage, shows that at +51 C. the cumene disproportionated smoothly to form essentially pure meta di-isopropylbenzene and 1,3,5-tri-isopropy1benzene. (In runs 2-7, the tri-derivative was, within the error of the infrared method, the pure 1,3,5-isomer.) The long contacting time of 30 minutes at this temperature produced a product containing about 2 moles of the tri-derivative per mole of the di-derivative.

Run 3, which is like run 2 except for a lower temperature of +14 C., gave a product wherein the ratio of dito triderivatives is about 2, i. e., just the reverse of the distribution of run 2.

Run 4 was carried out at C. and shows that, even with a minute time, at this temperature no tri-derivative was formed. The di-derivative was virtually pure meta di-isop ropylbenzene.

Runs 5 and 6 were carried out to show the influence of time, at constant temperature,on the product distribution. In run 5, no tri-derivative was found, at a 5 minute contact time at 5 C. contacting temperature. However, the 30 minute time in run 6 gave a significant yield of the tri-derivative. These runs indicate the need for coordinating both temperature and time in carrying out the process.

Run 7 was carried out with sec-butylbenzene. The product distribution in this run is substantially the same as the cumenc in run 3. Infrared analysis of themderivative indicated it to have the 1,3,5 orientation. This new compound 1,3,5-tri-secondary butylbenzene has This application is a division of our copending application, Serial Number 389,328, filed October 30, 1953, now Patent No. 2,852,575.

Thus having described the invention, what is claimed is:

1. An isomerization process which comprises (1) contacting, under substantially anhydrous conditions and in the substantial absence of reactive hydrocarbons, polysecondary alkylbenzene containing at least 2 secondary alkyl groups, which groups are selected from the class consisting of isopropyl and secondary butyl, with (a) (i) at least sufficient liquid HF to form a distinct acid phase and (:1) (ii) with at least one mole of BF per mole of poly-secondary alkylbenzene charged, at a temperature at set out in the annexed schedule for a time such that the poly-secondary alkylbenzene charged is isomerized substantially to the meta-oriented isomer and substantially no disproportionation reactions occur, and (2) removing HF and BF under conditions to substantially avoid rearrangement reactions and (3) recovering from the hydrocarbon reaction product a poly-secondary alkylbenzene fraction comprising substantially the meta-oriented isomer of the poly-secondary alkylbenzene charged, wherein the relationship of the type of poly-secondary alkylbenzene charged and the temperature of contacting is set out in the annexed schedule:

Poly-secondary alkylbenzene charged: Temperature, C.

I. Ortho di-, para di-, mixtures thereof, and mixtures of meta diand a substantial amount of at least one other isomer VII 12 III. A tri-isomer other than the 1,3,5-tri-isomer and mixtures of the 1,3,5-tri'-isomer and a substantial amount of at least one other isomer of tri- 0 to +30 2. An isomerization process which comprises contacting, under substantially anhydrous conditions and in the substantial absence of reactive hydrocarbons, a di-secondary alkylbenzene selected from the class consisting of the ortho isomer, the para isomer, mixtures thereof and mixtures of the meta isomer and a substantial amount of at least one other isomer of di-isopropylbenzene and di-secondary butylbenzene, with at least 1 mole of BF per mole of di-s'econdary alkylbenzene charged and at least sufiicient liquid HF to form a distinct acid phase, at a temperature of not more than about 30 C. for a time of not more than about 30 minutes, wherein the lower the temperature of contacting the longer the permis sible time of contacting, and removing HF and BF from said acid phase under conditions to substantially avoid rearrangement reactions and recovering from the reaction product a di-secondary alkylbenzene fraction comprising substantially the meta isomer.

3. The process of claim 2 wherein the temperature is about -30 C. and the time is not more than about 5 minutes and said reaction product contains essentially no poly-secondary alkylbenzene.

4. The process of claim 2 wherein said secondary alkylbenzene is para-di-isopropylbenzene.

5. An isomerization process which comprises contacting, under substantially anhydrous conditions, a charge comprising essentially (i) at least a substantial amount of benzene and (ii) only one di-secondary alkylbenzene selected from the class consisting of the ortho isomer, the paraisomer, mixtures thereof and mixtures of the meta isomer and a substantial amount of at least one other isomer of di-isopropylbenzene and di-secondary butylbenzene, with at least 1 mole of BF;; per mole of secondary alkylbenzene charged and at least sufiicient liquid HP to form a distinct acid phase, at a temperature between about .30 C. and about -5 C. for a time at least sufiicient to isomerize said secondary alkylbenzene essentially to the meta isomer but not long enough to form appreciable amounts of disproportionation product, and removing HF and BF from said acid phase under conditions to essentially avoid disproportionation reactions and recovering a di-secondary alkylbenzenefraction consisting essentially of the meta isomer.

6. The process of claim 5 wherein the amount of benzene in said charge is between about 1 mole per mole of di-secondary alkylbenzene and the limit of solubility in said acid phase.

7. The process of claim 5 wherein the maximum time of contacting is between about 5 minutes at -5 C. and about 2 hours at --20 C., the longer times corresponding to the lower temperatures.

8. The process of claim 5 wherein said acid phase is contacted with at least about 1 mole of a displacer per mole of secondary alkylbenzene present in said acid phase and substantially simultaneously thereafter with an amount of an inert liquid hydrocarbon suflicient to extract from said acid phase displaced secondary-alkylbenzene, under conditions of temperature and time such that substantially no rearrangement reaction takes place, and separating a separate rafiinate phase comprising inert hydrocarbon and secondary alkylbenzene from an acid phase comprising HF, BF displacer and some secondary alkylbenzene, and recovering from said raffinate phase a secondary alkylbenzene comprising essentially the meta isomer, and wherein said displacer is a poly-alkylbenzene containing at least 3 alkyl groups that are selected from the class consisting of normal and secondary, which contain not more than 4 carbon atoms.

9. The process of claim 8 wherein said inert hydrocarbon is present in an amount between about 50 and '13 500 volume percent based on secondary alkylbenzene in said acid phase.

10. An isomerization process which comprises contacting, under substantially anhydrous conditions and in the substantial absence of reactive hydrocarbons, a tri-secondary alkylbenzene selected from the class consisting of an isomer other than the 1,3,5-isomer and mixtures of the 1,3,5-isomer and a substantial amount of at least one other isomer of tri-isopropylbenzene and tri-secondary butylbenzene, with at least 1 mole of BF;, per mole of 10 tri-secondary alkylbenzene charged and at least suflicient liquid HP to form a distinct acid phase, at a temperature of between about 0 and +30 C. for a time sufliciently short to substantially avoid disproportionation reactions, and removing HF and BF;, from said acid phase under conditions to substantially avoid rearrangement reactions 5 sists essentially of at least one isomer of tri-isopropylbenzene other than the 1,3,5-isomer.

References Cited in the file of this patent UNITED STATES PATENTS McCaulay et al Apr. 10, 1956 OTHER REFERENCES Siderova et 211.: Zhur. Obshchei Khim. (J. Gen. Chem.),

15 vol. 19, pages 337-41 (1949); abstracted in Chem. Ab-

stracts, vol. 43, 6582-3 (1949). 

1. AN ISOMERIZATION PROCESS WHICH COMPRISES (1) CONTACTING, UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS AND IN THE SUBSTANTIAL ABSENCE OF REACTIVE HYDROCARBONS, POLYSECONDARY ALKYLBENZENE CONTAINING AT LEAST 2 SECONDARY ALKYL GROUPS, WHICH GROUPS ARE SELECTED FROM THE CLASS CONSISTING OF ISOPROPYL AND SECONDARY BUTYL, WITH (A) (1) AT LEAST SUFFICIENT LIQUID HF TO FORM A DISTINCT ACID TO PHASE AND (A) (II) WITH AT LEAST ONE MOLE OF BF3 PER MOLE OF POLY-SECONDARY ALKYLBENZENE CHARGED, AT A TEMPERATURE AT SET OUT IN THE ANNEXED SCHEDULE FOR A TIME SUCH THAT THE POLY-SECONDARY ALKYLBENZENE CHARGED IS ISOMERIZED SUBSTANTIALLY TO THE META-ORIENTED ISOMER AND SUBSTANTIALLY NO DISPROPORTIONATION REACTIONS OCCUR, AND (2) REMOVING HF AND BF3 UNDER CONDITIONS TO SUBSTANTIALLY AVOID REARRANGEMENT REACTIONS AND (3) RECOVERING FROM THE HYDROCARBON REACTIONS PRODUCT A POLY-SECONDARY ALKLBENZENE FRACTION COMPRISING SUBSTANTIALLY THE META-ORIENTED ISOMER OF THE POLY-SECONDARY ALKYLBENZENE CHARGED, WHEREIN THE RELATIONSHIP OF THE TYPE OF POLY-SECONDARY ALKYLBENZENE CHARGED AND THE TEMPERATURE OF CONTACTING IS SET OUT IN THE ANNEXED SCHEDULE: POLY-SECONDARY ALKYLBENZENE CHARGED: TEMPERATURE, *C. I. ORTHO DI-, PARA DI-, MIXTURES THEREOF, AND MIXTURES OF META DI- AND A SUBSTANTIAL AMOUNT OF AT LEAST ONE OTHER ISOMER OF DI-------------- LOWER THAN -30 II. A MIXTURE OF I AND AT LEAST A SUBSTANTIAL AMOUNT OF BENZENE -30 TO -5 III. A TRIS-ISOMER OTHER THAN THE 1,3,5-TRI-ISOMER OTHER THAN THE OF THE 1,3,5-TRI-ISOMER AND A SUBSTANTIAL AMOUNT OF AT LEAST ONE OTHER ISOMER OF TRI- 0 TO + 30 